This dissertation examines jury nullification - the ability of American juries in particular criminal cases to ignore or override valid law to be applied to defendants by acquitting them in cases in which the facts are undisputed or clear - as an exercise of sovereignty over the friend-enemy distinction as those terms are defined by Carl Schmitt. It begins with a biography of Schmitt and a description of his concept of sovereignty as ultimate decisional power. It then discusses sovereignty in the American context, with particular attention to the principles of the Founding and the nature of the fictively constructed American people. It next applies Schmitt's concept of decisional sovereignty to the American context, concluding that sovereignty in America is diffuse, and its exercise by particular governmental actors is to some degree cloaked, and that the sovereignty of the American people, while crucial to the founding moment, is largely latent in ordinary times. This application of Schmitt to sovereignty in America also demonstrates the deep tension between democratic popular sovereignty and rule-of-law liberalism. The dissertation then turns to Schmitt's understanding of the distinction between friend and enemy as the central political axis, and argues that the criminal in the American context is functionally the enemy, if not the absolute enemy of the polity. It then discusses in detail the mechanics and history of jury nullification, ultimately concluding that jury nullification both operates at the crucial political moment at which enemies are generated (or not) through the application of criminal law to defendants, and is an act of popular sovereignty, intended by the Founders to help preserve a balance between democracy and liberalism by maintaining a central political role for the people.